drm: gma500: Replace drm_fb_get_bpp_depth() with drm_format_info()

The driver uses drm_fb_get_bpp_depth() to check whether it can support
the format requested by userspace when creating a framebuffer. This
isn't the right API, as it doesn't differentiate between RGB formats
other than on a depth and bpp basis.

Fixing this requires non trivial changes to the drivers internals. As a
first step, replace usage of the drm_fb_get_bpp_depth() function with an
equivalent check based on drm_format_info(). This is part of a wider
effort to remove usage of the drm_fb_get_bpp_depth() function in
drivers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1476744081-24485-9-git-send-email-laurent.pinchart@ideasonboard.com